Field of the Invention
The present invention relates to a lighting device and an image reading device and relates to the image reading device which optically reads reflected light from a document image and the lighting device used therein in detail.
Description of the Related Art
An image reading device referred to as a scanner in general two-dimensionally reads a document image by moving a reading system including a lighting device extending in a main scanning direction or a target to be read such as a document in a sub scanning direction. Conventionally, a fluorescent light is widely used as this type of the light source; recently, however, this is often replaced with an LED for saving power. However, the LED is a point light source different from the fluorescent light. Therefore, a light guide body disclosed in U.S. Pat. No. 8,279,499 is commonly used in the lighting device using the LED as the light source for obtaining line-shaped light distribution required for scanning. It is desired to improve a ratio of a light amount of a right beam emitted from the light guide body to the target to be read to the light amount of the light beam emitted from the LED, that is to say, extraction efficiency of the light beam in the lighting device provided with this type of light guide body (hereinafter, referred to as conventional lighting device).